Drill cuttings are a by-product of drilling deep bores, such as are required by the oil and gas exploration and production industry to access hydrocarbon reservoirs. The drill cuttings are separated from the drilling fluid or mud used to carry the cuttings to surface and are then stored at the drilling location. At intervals the cuttings are collected and transported for treatment and disposal.
Conventionally, in offshore drilling operations, drill cuttings are stored in portable containers or skips. The filled skips are moved by crane between the drilling rig and a supply boat used to transport the cuttings to shore for treatment and disposal. However, operators would prefer to avoid the large number of crane movements necessary to move any volume of drill cuttings, the operation having health and safety implications and being vulnerable to disruption due to adverse weather conditions.
Other methods of storing and conveying drill cuttings have been proposed, as described in WO 00/76889. This document describes the use of a pressure vessel including a conical hopper portion. The cone angle of the hopper portion is selected to be less than a critical value required to achieve mass flow, which is described as the material descending as a mass in a uniform way towards the outlet with all the material moving. When compressed gas is applied to the drill cuttings in the vessel, the material flows out of the vessel.